Improvements in and relating to remote sensing

Abstract

A system for remotely sensing light emanating from within a monitored environment. The system comprises one or more retro-reflective optical elements bearing a reflective optical coating upon a surface thereof and positionable within the environment to be monitored. A light source is arranged to direct a beam of light at the optical element(s), and a detector is arranged to receive from the optical element(s) light returned by the optical coating in response to the beam of light and to detect a property of the monitored environment according to said returned light. The optical element(s) includes a body comprising a core part of positive optical power and clad by a cladding part. The refractive index of the core is greater than that of the cladding. The optical coating is arranged over the cladding to receive light which has been at least partially converged by the core part for subsequent retro-reflection.

Description

FIELD OF THE INVENTION[0001]The invention relates to remote sensing systems and methods. In particular, though not exclusively, the invention relates to free-space optical methods of remote sensing.BACKGROUND[0002]Conventional free-space optical remote sensing techniques rely on irradiating a monitored environment, with light intended to interact with that environment in a manner which produces a detectable change. In particular, by analysing the light that has been backscattered by target molecules within the monitored environment, such as water molecules, information about the state of those molecules may be gleaned. By inference, one may deduce the state of the environment of which those molecules form a part. For example, spectral shifts in the optical frequency of return optical signals resulting from inelastic optical interactions with a target molecule may be detected. These shifts can be either to a lower frequency (Stokes) or to a higher frequency (Anti-Stokes). By using a ...

AI Technical Summary

Benefits of technology

The invention is about a system and method for remotely sensing using retro-reflective optical elements placed in an environment to be monitored. These optical elements are illuminated by a remote light source and the retro-reflected light is detected for analysis. The invention proposes using a retro-reflective optical element with an embedded core having a high refractive index and a cladding with a lower refractive index. This results in efficient convergence of the incident light towards the reflective optical coating and enhances the efficiency of retro-reflection. The optical elements may also contain a photo-luminescent material that can be remotely excited and the retro-reflective action of the optical element permits efficient return of the photo-luminescent light generated by the material. The photo-luminescent response of the material is preferably variable according to changes in the monitored property of the environment.

Problems solved by technology

This makes the Raman technique more difficult to utilise in environments where transmission windows are restricted (e.g. underwater).

Consequently, Raman techniques are limited in their use.

Remote sensing techniques such as Brillouin and Raman lidar methods tend to be limited by the very low levels of molecular backscatter they produce in a monitored environment, in use.

However, this method depends upon to ability to place a physically steady and controllable light source in a desired location and, clearly, this may not be possible or desirable in some circumstances, especially in marine environments.

Images